1. Field of the Invention
The present invention relates to a device for the selective propulsion or movement of a well tool. More particularly, it relates to a device for controlling the movement of a well tool which is used in petroleum wells in connection with the recovery of petroleum products or servicing/intervention in petroleum wells. The movement in the form of propulsion and/or rotation of the well tool is provided by means of magnetic forces. The invention also relates to a method for the selective movement of a well tool in or through at least a portion of a pipe string.
By the concept well tool is meant herein any equipment which is arranged to be run into and operated within a well in connection with the operation and servicing thereof.
2. Description of the Related Art
According to prior art a well tool is run into the well by being lowered, under the influence of gravity, into the well, hanging on, for example, a steel rope, a so-called “wireline”. In portions of the well, in which gravity cannot be utilized to drive the tool into the well, propelling devices may be used, such as so-called well tractors, pulling or pushing the tool in the longitudinal direction of the well. In some cases so-called coiled tubing is also used to drive the well tool to its location of use.
There are several drawbacks related to the prior art mentioned above.
The above-mentioned prior art is based on there being a physical connection between the well tool and a portion of the well located on the surface. To prevent leakages from the well into the atmosphere, extensive surface lock-gate tools are required. In addition extensive run-in equipment is required and a manning of 2 to 10 persons, depending on what equipment is to be run into the well. In addition, the area at the well surface is considered to be a hazardous area for personnel because of pressurized equipment, movable parts and the lifting and moving of heavy equipment.
Due to the extensive equipment required and the hazards connected with the above-mentioned prior art operations, it is a time-consuming process to install the well tool and pressure test the surface pressure control system of the well. This entails that the production from the well will have to be shut down for a relatively long time. Additionally, for reasons of safety, it may be necessary to shut down wells located in the area where heavy equipment is being lifted.
The invention has as its object to remedy or at least reduce one or more drawbacks of the prior art.